Skip to content

Boboyan Batholith EarthCache

Hidden : 09/23/2008
1.5 out of 5
3 out of 5

Size: Size:   other (other)

Join now to view geocache location details. It's free!


How Geocaching Works

Please note Use of services is subject to the terms and conditions in our disclaimer.

Geocache Description:

From the trailhead, walk west along the well formed and marked trail to the Boboyan trig. Along the way, and especially at the trig, you will find a lot of shale type rock where rocks of the Ordovician period are metamorphosed (cordierite hornfels). This happens where they collide with the Granodiorite pluton (which looks like granite) of the Murrumbidgee Batholith.

Rock becomes metamorphosed when it is subjected to elevated pressures and temperatures. In a continent-continent collision, mountain-building forces bury rock many kilometres beneath the earth's surface. The weight of the overlying rock subjects the buried rock to enormous pressures. The internal heat of the earth gradually heats the buried' rock to extremely high temperatures. Under these conditions, the minerals in the buried rock react chemically with each other to form new mineral assemblages.

The original composition of the rock, together with the temperature and pressure to which it is subjected, determines what kind of metamorphic rock will form.

At the posted coordinates you will find yourself at the top of the pluton outcrop overlooking spectacular granite tor views! There is also a sign talking about the boundary between the two types of rock!

To log this cache, you will need to answer the following questions:
1. Which is older – the granite or the shale?
2. How many millions of years older?
3. What is the distance from the sign to the granite boulders behind you?

Feel free to post pictures of the magnificent views, the granite, or the masses of shale, but do not post any pictures that will help provide answers to the above! 

Additional Hints (No hints available.)